1. Field of the Invention
The present invention relates to transit vehicle window systems and, more particularly, to window systems intended for use in urban transit vehicles subject to vandalism and graffiti.
2. Description of Related Art
Window systems for transit vehicles used in urban areas typically include an exterior window glazing that can be readily replaced and a sacrificial layer or shield positioned on the inside of the vehicle to allow the glazing or sacrificial layer to be replaced in the event of vandalism or graffiti. For instance, scratch type graffiti can be mitigated simply by replacing the sacrificial layer. Further, if the window glazing is broken, the glazing can be replaced quickly resulting in significant reductions in vehicle downtime.
Referring to FIG. 1, in the North American market, windows 2 are generally affixed to the vehicle using a clamping ring 4 and a series of mechanical fasteners. The vehicle structure 6 is sandwiched or compressed between a main frame 8 of the window 2 and the clamping ring 4. The vehicle structure 6 and the window 2 define an outside 10 and an inside 12 of the vehicle.
In other markets outside of North America, such as Europe, the United Kingdom and Australia, operators are faced with similar graffiti and vandalism issues. However, in these markets, the method and arrangements of urban transit vehicle manufacturing is somewhat different. Referring to FIG. 2, these markets typically utilize what is referred to as “bonded glazing” 14, which directly bonds the vehicle glazing 16 to the vehicle structure 18 via a vehicle glazing adhesive 20. The interior is typically finished using interior vehicle trim 22.
In the interest of ensuring a relatively quick turn-around of transit vehicles that have had windows broken, the primary contract transportation providers for cities may specify that rubber gasket glazed window arrangements are to be used. Although the rubber gasket glazed window arrangements feature a more rapid turn-around time than the bonded glass counterpart, the exterior aesthetic of the vehicle is less appealing. With regard to interior window surface graffiti, an adhesive backed, biaxially-oriented polyethylene terephthalate (boPET) polyester film (sold commercially under the name MYLAR and equivalent products) is commonly used to protect the interior of the window. The boPET polyester film is used in single sheet applications as well as “tear-away”, multi-sheet applications. The boPET polyester film can be replaced when subjected to graffiti or vandalism rather than replacing the glass. The application of the boPET polyester an, however, is a specialized skill acquired over time. The film is difficult for a novice to apply without wrinkles or trapped air bubbles. The combination of the specialized skill in applying and the material cost of the film can result in high maintenance costs.
U.S. Pat. Nos. 7,152,906; 7,080,874; and 6,869,128 (“Farrar et al., quick change window assembly patents”) generally disclose quick change window assemblies allowing for the easy removal and replacement of window glazing from the window opening in the sidewall of the vehicle and are hereby incorporated by reference in their entirety.
U.S. Pat. Nos. 6,205,723; 6,408,574; 6,425,215; 6,688,044; 6,871,902; 7,021,006; 7,082,736; and 7,254,927 (“Farrar et al., quick release sacrificial shield patents”) generally disclose quick release sacrificial shield arrangements for window assemblies and are hereby incorporated by reference in their entirety.